The invention relates to a casting set for a diecasting machine. The casting set includes a casting chamber, and a casting plunger guided in the casting chamber. The casting plunger has a casting plunger rod operable by a casting drive. A lubricant feed line leading to the circumferential surface of the plunger is provided for the lubrication thereof. The feed line communicates with a lubricant channel formed as an annular groove extending around the casting chamber.
Prior art
A casting set in a casting unit of a diecasting machine, with casting-plunger lubrication to improve the quality of the diecastings, is known from the literature reference Ernst Brunhuber: Praxis der Druckgu.beta.fertigung [Practical Diecasting], third edition 1980, page 28 in conjunction with page 41 and pages 126, 127. Here, automatic lubrication of the casting plunger can be achieved by virtue of the fact that leading from a grease pump are lines to two, three or four holes at the casting chamber which open into an annular groove. The lubrication process is triggered by the machine control and metering of the quantity of lubricant is effected in a time-dependent manner. The disadvantage is that the pasty lubricant may go hard after pauses in operation and block the lines. Sprayable lubricants and parting agents are therefore said to be more favorable.
A device for the automatic lubrication of the casting plunger of a cold-chamber diecasting machine is likewise known from the further literature reference Swiss Patent 436,588. In this device, the lubricant is guided via radial holes through the casting-chamber wall to the inner circumferential surface of the casting chamber. Here, the three holes arranged symmetrically on the circumferential surface are closed by means of a spring-assisted spherical closure element. For this purpose, the spherical outer contour of the closure element projects into the cylinder space and is displaced radially outwards by the outer circumferential surface of the casting plunger in order to enable the flow of lubricant to the casting plunger.
This embodiment first of all has the same disadvantages as those described above with reference to the Brunhuber literature reference. By means of such an arrangement, it is furthermore possible for lubricant to emerge only at a number of points on the inner circumferential surface of the casting chamber. Uniform coating of the casting plunger with lubricant is therefore not possible with such an arrangement, which does not have an annular groove.
Fundamentally, the problem with the lubrication of the casting plunger in arrangements of this kind is the impossibility of precise and reproducible metering, particularly as the lubricant sticks due to the effect of the heat of the molten metal and solidifies particularly at inaccessible points, with the result that lubrication of the casting plunger is nonuniform.
German Auslegeschrift 2,162,186 has furthermore disclosed automatic oil spray lubrication for the casting plunger of a cold-chamber diecasting machine in which the plunger rod of the casting set is penetrated by a through hole or a passage through which lubricant is fed to the casting plunger. Here, as described in Brunhuber, page 127, sprayable lubricants are used, these being dispensed onto the inner wall of the casting chamber by means of spray nozzles directly behind the casting plunger. In this way, the sprayable lubricant in this known device in accordance with the German Auslegeschrift is applied directly to the inner wall of the casting chamber by the plunger rod and distributed uniformly over the whole length of the casting chamber by the movement of the casting plunger.
However, such an arrangement for the application of lubricant entails high technical and constructional outlay since separate lines have to be laid through the casting plunger. To carry the lubricant on from the plunger rod to the lubricating assembly, flexible lines are required, and these must accompany the movement of the plunger. However, these hoses are absolutely undesirable particularly in the sector of metal metering. The circumferential surface of the casting plunger itself is furthermore not specifically lubricated. Lubrication is accordingly accomplished by spraying the inner wall of the casting chamber.
A device for the pressurized lubrication of the plungers on diecasting machines with a vertically arranged casting chamber is known from German Utility Model DE-GM 1,939,227. Here, a lubricating block is mounted on the casting chamber in its upper region, this lubricating block forming an annular channel around the casting plunger, and the lubricant is fed to the annular channel via a lubricant feed line by means of a piston-type lubricant pump, a control cam controlling the amount of lubricant during the feed process.